I always knock first.

我一般会先敲下门。

youdao

It is not appropriate to walk into somebody's bedroom when the door is closed. You must always knock first.

当别人卧室门关上时不适合直接开门进去，你应该先敲敲门。

youdao

Knock first, then wait to be invited in.

应该先敲门，然后等待进入的邀请。

youdao

Knock first, then wait to be invited in.

应该先敲门，然后等待进入的邀请。

youdao